Help with water parameters?

My tank has 0ppm nitrite and ammonia and 5ppm nitrate, so, pretty damn good (if I do say so myself), but I can't get the pH any lower than 7.6! It was 7.6 earlier, and I added 60 drops of pH down (the recommended amount) and it's STILL 7.6! What do I do? Do I add MORE pH down? My water kit stops at 7.6 for pH and starts at 7.6 for high range pH, so I did both tests to make sure.